{
 "metadata": {
  "name": "9932_02_02"
 },
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   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Chapter 2, example 2\n",
      "====================\n",
      "\n",
      "Here we continue with the previous example: we write some Python commands to list all files in the downloaded data. We also show how to execute external Python scripts in IPython using the magic command `%run`.\n",
      "\n",
      "The following code should be stored in `egos.py`:\n",
      "\n",
      "    import sys\n",
      "    import os\n",
      "    # we retrieve the folder as the first positional argument\n",
      "    # to the command-line call\n",
      "    if len(sys.argv) > 1:\n",
      "        folder = sys.argv[1]\n",
      "    # we list all files in the specified folder\n",
      "    files = os.listdir(folder)\n",
      "    # ids contains the sorted list of all unique idenfitiers\n",
      "    ids = sorted(set(map(lambda file: int(file.split('.')[0]), files)))\n"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "The `egos.py` script accepts the facebook folder's relative path as an argument, and extracts all file identifiers in an `ids` variable. Each file in the dataset has the form `ID.extension`."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%run egos.py data/facebook"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "After using the `%run` command to execute this script, all variables defined in the script are available in the current user namespace. In particular, we can retrieve the `ids` variable here."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "ids"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 2,
       "text": [
        "[0, 107, 348, 414, 686, 698, 1684, 1912, 3437, 3980]"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Whereas output variables are available in the namespace *after* the script's execution, variables available in IPython *before* its execution are not available within the script by default. For example, here we define the `folder` variable in the current namespace, and we call `%run egos.py` without an argument."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "folder = 'data/facebook'"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 3
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "A `NameError` exception is expected here, because the `folder` variable is not defined in the script, although it is defined in the current namespace."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%run egos.py"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "ename": "NameError",
       "evalue": "name 'folder' is not defined",
       "output_type": "pyerr",
       "traceback": [
        "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[1;31mNameError\u001b[0m                                 Traceback (most recent call last)",
        "\u001b[1;32mIPython\\utils\\py3compat.pyc\u001b[0m in \u001b[0;36mexecfile\u001b[1;34m(fname, glob, loc)\u001b[0m\n\u001b[0;32m    169\u001b[0m             \u001b[1;32melse\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    170\u001b[0m                 \u001b[0mfilename\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mfname\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m--> 171\u001b[1;33m             \u001b[1;32mexec\u001b[0m \u001b[0mcompile\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mscripttext\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mfilename\u001b[0m\u001b[1;33m,\u001b[0m \u001b[1;34m'exec'\u001b[0m\u001b[1;33m)\u001b[0m \u001b[1;32min\u001b[0m \u001b[0mglob\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mloc\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m    172\u001b[0m     \u001b[1;32melse\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m    173\u001b[0m         \u001b[1;32mdef\u001b[0m \u001b[0mexecfile\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mfname\u001b[0m\u001b[1;33m,\u001b[0m \u001b[1;33m*\u001b[0m\u001b[0mwhere\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n",
        "\u001b[1;32mchapter2\\egos.py\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m      6\u001b[0m     \u001b[0mfolder\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0msys\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0margv\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;36m1\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      7\u001b[0m \u001b[1;31m# we list all files in the specified folder\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 8\u001b[1;33m \u001b[0mfiles\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mos\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mlistdir\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mfolder\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m      9\u001b[0m \u001b[1;31m# ids contains the sorted list of all unique idenfitiers\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m     10\u001b[0m \u001b[0mids\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0msorted\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mset\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mmap\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;32mlambda\u001b[0m \u001b[0mfile\u001b[0m\u001b[1;33m:\u001b[0m \u001b[0mint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mfile\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0msplit\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;34m'.'\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;36m0\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mfiles\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n",
        "\u001b[1;31mNameError\u001b[0m: name 'folder' is not defined"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "However, we can tell IPython *explicitely* to use the current user namespace for the external script's execution with the `-i` option."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%run -i egos.py"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 5
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Now the script's execution works as expected, and the `ids` variable is available."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "ids"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "pyout",
       "prompt_number": 6,
       "text": [
        "[0, 107, 348, 414, 686, 698, 1684, 1912, 3437, 3980]"
       ]
      }
     ],
     "prompt_number": 6
    }
   ],
   "metadata": {}
  }
 ]
}